Conventionally, a scribed circle test is well-known in a real forming or a model forming by plastic working of steel as a method for examining a deformation state and a deformation path and for measuring rupture limit strain and wrinkle limit strain of material.
In the scribed circle test, a pattern (circle or grid-like pattern, for example) configured by arranging a plurality of unit graphics is drawn as an index pattern on a surface of a test piece as a workpiece in advance. The examination of the deformation of the test piece and the measurement of the strain of the test piece are performed by measuring a form change of each unit graphic before and after the forming of the test piece.
Japanese Patent Application Publication No. 2001-280934 discloses an invention related to the drawing of an index pattern on a surface of a test piece. The invention described above is configured to draw the index pattern, in which a plurality of circles is arranged, on an outer surface of a metallic pipe by a laser marking device. Since the invention described above is configured to draw the index pattern on the outer surface of the metallic pipe by emitting a laser beam from the laser marking device, a sharp index pattern which is indelible during the machining of the test piece can be drawn unlike in the case of drawing the index pattern with a stamp and ink.